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First published online February 1, 2008
Journal of Experimental Biology 211, 630-641 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.008565
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Swelling-activated chloride channels in leech Retzius neurons

Philippe Coulon*, Hans-Joachim Wüsten, Peter Hochstrate and Paul Wilhelm Dierkes{dagger}

Institut für Neurobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany

* Author for correspondence at present address: Institute for Physiology I (Neurophysiology), Robert-Koch-Straße 27a, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany (e-mail: coulon{at}uni-muenster.de)

Accepted 18 December 2007

During periods of high activity neurons are expected to swell due to the uptake of Cl–. To find out whether leech Retzius neurons possess swelling-activated Cl– channels that facilitate Cl– efflux and, hence, volume recovery, we exposed the cells to hypotonic solutions. In hypotonic solutions, the cells slowly swelled but did not undergo a regulatory volume decrease. However, the cell volume increased less than predicted for an ideal osmometer, suggesting the action of a compensatory mechanism. The cell swelling was paralleled by a marked decrease in the input resistance as well as by the activation of a membrane current with a reversal potential close to the Cl– equilibrium potential. This current was substantially diminished by removing bath Cl–, by applying the Cl– channel blocker DIDS, or by treating the cells with the tubulin polymerization inhibitor colchicine. Furthermore, in the presence of colchicine or vinblastine, the cell swelling was substantially increased. It is concluded that leech Retzius neurons possess swelling-activated Cl– channels that require an intact microtubule system for activation. The channels may help to restore cell volume after periods of high neuronal activity.

Key words: Hirudo medicinalis, osmotic shock, Retzius neuron, chloride channel, volume regulation






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